1. Field of the Invention
The present invention relates to an ink jet printer, and more particularly, to an ink jet printhead carrier and one or more ink jet printhead assemblies associated therewith.
2. Description of the Related Art
Typical ink jet printers include a printer frame which defines a media path for a sheet of media. A sheet of print media is transported by a series of rollers along the media path through a print zone. In the print zone, one or more printheads eject ink onto the sheet at predefined locations to form an image thereon. The quality of the formed image is dependent, at least in part, on the tolerances and alignment of various components in the printing system.
Such a typical ink jet printer includes a printhead carrier for carrying the one or more printheads. The ink jet printer also includes one or more guide rods mounted to the printer to be positioned transverse to the direction of media travel. The guide rods guide the printhead carrier for reciprocating movement across the width of the sheet of print media. Typically, each printhead is mounted into a cradle within the printhead carrier. The carrier includes fixed bearings which contact a guide surface of each of the one or more guide rods.
Although this approach can provide adequate printing results, such an arrangement induces positioning and alignment errors between the physical location of the print nozzles of the printhead in relation to the position of the printhead carrier, and in relation to the one or more guide rods which position and support the printhead carrier. Such positioning and alignment errors translate into errors between the calculated location on the sheet of print media at which an ink dot is to be placed and the actual location at which the ink dot is placed, which in turn translates into decrease print quality.
In one aspect of the invention, an imaging apparatus includes a first side frame and a second side frame. A first guide rod extends between the first side wall and the second side wall and has a first surface and a first cross-sectional area. A second guide rod extends between the first side frame and the second side frame and is arranged parallel to the first guide rod. The second guide rod has a second surface and a second cross-sectional area. The imaging apparatus also includes a carrier assembly having a body, and a printhead interface unit attached to the body. A printhead unit is structured and adapted for mating engagement the printhead interface unit. The printhead unit has at least one bearing surface which contacts the first surface of the first guide rod and at least one second bearing surface which contacts the second surface of the second guide rod.
In another aspect of the invention, an imaging apparatus includes a first side frame and a second side frame. A first guide rod extends between the first side wall and the second side wall, wherein the first guide rod has a first surface and a first cross-sectional area. A second guide rod extends between the first side frame and the second side frame and is arranged parallel to the first guide rod. The second guide rod has a second surface and a second cross-sectional area. The imaging apparatus also includes a carrier assembly having a body, and a color printhead interface unit attached to the body. A color printhead unit is structured and arranged for mating engagement with the color printhead interface unit. The color printhead unit has a first bearing surface which contacts the first surface of the first guide rod and a first pair of V-shaped bearings defining four bearing surfaces which contact the second guide surface of the second guide rod.
Another aspect of the invention is a printhead unit for an imaging apparatus having a guide member. The printhead unit includes a housing, a printhead attached to the housing and at least one bearing having at least one bearing surface. The bearing is coupled to the housing and is positioned to engage the guide member.
Another aspect of the invention provides a printhead unit for an imaging apparatus having a first guide member and a second guide member. The printhead unit includes a housing; a printhead attached to the housing; a first bearing having a first bearing surface, the first bearing being coupled to the housing and positioned to engage the first guide member; and a second bearing having a second bearing surface, the second bearing being coupled to the housing and positioned to engage the second guide member.
An advantage of the present invention is that the carrier assembly is positioned relative to at least one printhead unit, thereby reducing positioning and alignment errors between the printhead unit and the carrier assembly.
Another advantage of the invention is that each printhead unit is directly positioned relative to the guide rod(s) of the imaging apparatus by locating guide rod bearings on each printhead unit, thereby eliminating the carrier as a factor in positioning and alignment errors between the printhead unit and the guide rod(s).